Experimental investigation on the nearshore transport of buoyant microplastic particles. (February 2023)

• Record Type: Journal Article
• Authors: Larsen, Bjarke Eltard; Al-Obaidi, Mustafa Ali Abdullah; Guler, Hasan Gokhan; Carstensen, Stefan; Goral, Koray Deniz; Christensen, Erik Damgaard; Kerpen, Nils B.; Schlurmann, Torsten; Fuhrman, David R.
• Is Part Of: Marine pollution bulletin. Volume 187(2023)
• Publication Date: 2023-02
• Subjects: Microplastic particles -- Buoyant particles -- Lagrangian transport velocities -- Breaking waves -- Non-breaking waves; Marine pollution -- Periodicals; Marine Biology -- Periodicals; Water Pollution -- Periodicals; Mer -- Pollution -- Périodiques; Publications périodiques; Pollution des mers; Lutte antipollution; Electronic journals; 363.7394
• DOI: 10.1016/j.marpolbul.2023.114610
• Languages: English
• ISSNs: 0025-326X

Abstract

Abstract: This paper presents experimental measurements of beaching times for buoyant microplastic particles released, both in the pre-breaking region and within the surf zone. The beaching times are used to quantify cross-shore Lagrangian transport velocities of the microplastics. Prior to breaking the particles travel onshore with a velocity close to the Lagrangian fluid particle velocity, regardless of particle characteristics. In the surf zone the Lagrangian velocities of the microplastics increase and become closer to the wave celerity. Furthermore, it is demonstrated that particles having low Dean numbers (dimensionless fall velocity) are transported at higher mean velocities, as they have a larger tendency to be at the free-surface relative to particles with higher Dean numbers. An empirical relation is formulated for predicting the cross-shore Lagrangian transport velocities of buoyant microplastic particles, valid for both non-breaking and breaking irregular waves. The expression matches the present experiments well, in addition to two prior studies. Graphical abstract: Unlabelled Image Highlights: Experiments show that buoyant microplastic particles are transported onshore by waves until they are eventually beached. Prior to breaking the microplastic transport velocity is near that of the fluid, regardless of particle characteristics. In the surf zone the Lagrangian particle transport velocities increase, becoming closer to the breaking wave celerity. Beneath breaking waves particles with high (low) rise velocities have larger (smaller) Lagrangian transport velocities. An equation predicting wave-induced transport velocity of buoyant microplastics across the coastal profile is provided.